Database Sharding with Incorporated Updates

ABSTRACT

In one embodiment, a method includes receiving an update of activity associated with one or more content objects associated with a search term. The content objects associated with the search term are indexed on a list of one or more index servers or a term server. The list of the term server include identifier information of one or more content object types. The list of the index servers include identifier information of a single content object type. The method also includes determining whether the search term has a number of associated content objects exceeding a pre-determined threshold number; and modifying the list associated with the search term of a term server or one or more of the index servers based at least in part on the determination and in response to the update.

TECHNICAL FIELD

This disclosure generally relates to search algorithms.

BACKGROUND

A social-networking system, which may include a social-networkingwebsite, may enable its users (such as persons or organizations) tointeract with it and with each other through it. The social-networkingsystem may, with input from a user, create and store in thesocial-networking system a user profile associated with the user. Theuser profile may include demographic information, communication-channelinformation, and information on personal interests of the user. Thesocial-networking system may also, with input from a user, create andstore a record of relationships of the user with other users of thesocial-networking system, as well as provide services (e.g. wall posts,photo-sharing, event organization, messaging, games, or advertisements)to facilitate social interaction between or among users.

The social-networking system may transmit over one or more networkscontent or messages related to its services to a mobile or othercomputing device of a user. A user may also install softwareapplications on a mobile or other computing device of the user foraccessing a user profile of the user and other data within thesocial-networking system. The social-networking system may generate apersonalized set of content objects to display to a user, such as anewsfeed of aggregated stories of other users connected to the user.

SUMMARY OF PARTICULAR EMBODIMENTS

In particular embodiments, a two-pronged architecture of index serversfor reducing database load may be provided for querying against adatabase. A first prong (the “term-sharded” (TS) index) of thearchitecture may include search terms having N or fewer search results(i.e. a short posting list), wherein the servers may include identifiersfor documents of all types (organized by type). A second prong of thearchitecture may provide a plurality of “doc-sharded” (DS) indices forthose search terms having greater than N search results (i.e. a longposting list), wherein each DS index only contains identifiers fordocuments of one or more particular types (e.g., photos, users,comments, likes, check-ins). When a complex query is received, a topaggregator may look up each search term in the query to determinewhether each term has a long posting list or a short posting list. Thetop aggregator may then accesses the TS index for terms with a shortposting list and the DS indices for terms with a long posting list. Forexample, a search for “Gangnam Style” may comprise two search terms(“Gangnam” and “Style”)—wherein “Gangnam” has a short posting list and“Style” has a very long posting list. In this case, a first posting listfor “Gangnam” may be pulled from the TS index and a second posting listfor “Style” may be pulled from the DS indices (across all relevantdocument types), and then the intersection of the two sets of documentidentifiers may be calculated to determine the actual set of searchresults.

When documents associated with a new term first begin to appear in thesocial graph, a posting list may be generated for the new term in the TSindex, as long as the length of the posting list is less than N. Entriesin the posting list may be marked with a document type. Once the lengthof the posting list exceeds N, chunks of the posting list aredistributed into the DS index in accordance with the document types ofitems in the posting list. If failover occurs during promotion, thenewly-live server may query the TS index for the promoted terms. Onceall of the pieces have been verified as successfully created in therelevant DS indices, the term and its posting list may be deleted fromthe TS index.

Any newly-added terms are added to the TS index together with a postinglist. Any newly-added document results are added to the TS index and/orDS indices as appropriate—if the newly-added document results triggerpromotion, then promotion may also be handled at this point. Any deleteddocument results are broadcast across the TS index and the DS indices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example network environment associated with asocial-networking system.

FIG. 2 illustrates an example partitioning of an example search index ofa social-networking system.

FIG. 3 illustrates an example method for an example search with anupdate layer.

FIG. 4 illustrates an example method for an example search withincorporated updates.

FIG. 5 illustrates an example social graph.

FIG. 6 illustrates an example computing system.

DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 illustrates an example network environment 100 associated with asocial-networking system. Network environment 100 includes a clientsystem 130, a social-networking system 160, and a third-party system 170connected to each other by a network 110. Although FIG. 1 illustrates aparticular arrangement of client system 130, social-networking system160, third-party system 170, and network 110, this disclosurecontemplates any suitable arrangement of client system 130,social-networking system 160, third-party system 170, and network 110.As an example and not by way of limitation, two or more of client system130, social-networking system 160, and third-party system 170 may beconnected to each other directly, bypassing network 110. As anotherexample, two or more of client system 130, social-networking system 160,and third-party system 170 may be physically or logically co-locatedwith each other in whole or in part. Moreover, although FIG. 1illustrates a particular number of client systems 130, social-networkingsystems 160, third-party systems 170, and networks 110, this disclosurecontemplates any suitable number of client systems 130,social-networking systems 160, third-party systems 170, and networks110. As an example and not by way of limitation, network environment 100may include multiple client system 130, social-networking systems 160,third-party systems 170, and networks 110.

This disclosure contemplates any suitable network 110. As an example andnot by way of limitation, one or more portions of network 110 mayinclude an ad hoc network, an intranet, an extranet, a virtual privatenetwork (VPN), a local area network (LAN), a wireless LAN (WLAN), a widearea network (WAN), a wireless WAN (WWAN), a metropolitan area network(MAN), a portion of the Internet, a portion of the Public SwitchedTelephone Network (PSTN), a cellular telephone network, or a combinationof two or more of these. Network 110 may include one or more networks110.

Links 150 may connect client system 130, social-networking system 160,and third-party system 170 to communication network 110 or to eachother. This disclosure contemplates any suitable links 150. Inparticular embodiments, one or more links 150 include one or morewireline (such as for example Digital Subscriber Line (DSL) or Data OverCable Service Interface Specification (DOCSIS)), wireless (such as forexample Wi-Fi or Worldwide Interoperability for Microwave Access(WiMAX)), or optical (such as for example Synchronous Optical Network(SONET) or Synchronous Digital Hierarchy (SDH)) links. In particularembodiments, one or more links 150 each include an ad hoc network, anintranet, an extranet, a VPN, a LAN, a WLAN, a WAN, a WWAN, a MAN, aportion of the Internet, a portion of the PSTN, a cellulartechnology-based network, a satellite communications technology-basednetwork, another link 150, or a combination of two or more such links150. Links 150 need not necessarily be the same throughout networkenvironment 100. One or more first links 150 may differ in one or morerespects from one or more second links 150.

In particular embodiments, client system 130 may be an electronic deviceincluding hardware, software, or embedded logic components or acombination of two or more such components and capable of carrying outthe appropriate functionalities implemented or supported by clientsystem 130. As an example and not by way of limitation, a client system130 may include a computer system such as a desktop computer, notebookor laptop computer, netbook, a tablet computer, e-book reader, GPSdevice, camera, personal digital assistant (PDA), handheld electronicdevice, cellular telephone, smartphone, other suitable electronicdevice, or any suitable combination thereof. This disclosurecontemplates any suitable client systems 130. A client system 130 mayenable a network user at client system 130 to access network 110. Aclient system 130 may enable its user to communicate with other users atother client systems 130.

In particular embodiments, client system 130 may include a web browser132, such as MICROSOFT INTERNET EXPLORER, GOOGLE CHROME or MOZILLAFIREFOX, and may have one or more add-ons, plug-ins, or otherextensions, such as TOOLBAR or YAHOO TOOLBAR. A user at client system130 may enter a Uniform Resource Locator (URL) or other addressdirecting the web browser 132 to a particular server (such as server162, or a server associated with a third-party system 170), and the webbrowser 132 may generate a Hyper Text Transfer Protocol (HTTP) requestand communicate the HTTP request to server. The server may accept theHTTP request and communicate to client system 130 one or more Hyper TextMarkup Language (HTML) files responsive to the HTTP request. Clientsystem 130 may render a webpage based on the HTML files from the serverfor presentation to the user. This disclosure contemplates any suitablewebpage files. As an example and not by way of limitation, webpages mayrender from HTML files, Extensible Hyper Text Markup Language (XHTML)files, or Extensible Markup Language (XML) files, according toparticular needs. Such pages may also execute scripts such as, forexample and without limitation, those written in JAVASCRIPT, JAVA,MICROSOFT SILVERLIGHT, combinations of markup language and scripts suchas AJAX (Asynchronous JAVASCRIPT and XML), and the like. Herein,reference to a webpage encompasses one or more corresponding webpagefiles (which a browser may use to render the webpage) and vice versa,where appropriate.

In particular embodiments, social-networking system 160 may be anetwork-addressable computing system that can host an online socialnetwork. Social-networking system 160 may generate, store, receive, andsend social-networking data, such as, for example, user-profile data,concept-profile data, social-graph information, or other suitable datarelated to the online social network. Social-networking system 160 maybe accessed by the other components of network environment 100 eitherdirectly or via network 110. In particular embodiments,social-networking system 160 may include one or more servers 162. Eachserver 162 may be a unitary server or a distributed server spanningmultiple computers or multiple datacenters. Servers 162 may be ofvarious types, such as, for example and without limitation, web server,news server, mail server, message server, advertising server, fileserver, application server, exchange server, database server, proxyserver, another server suitable for performing functions or processesdescribed herein, or any combination thereof. In particular embodiments,each server 162 may include hardware, software, or embedded logiccomponents or a combination of two or more such components for carryingout the appropriate functionalities implemented or supported by server162. In particular embodiments, social-networking system 164 may includeone or more data stores 164. Data stores 164 may be used to storevarious types of information. In particular embodiments, the informationstored in data stores 164 may be organized according to specific datastructures. In particular embodiments, each data store 164 may be arelational, columnar, correlation, or other suitable database. Althoughthis disclosure describes or illustrates particular types of databases,this disclosure contemplates any suitable types of databases. Particularembodiments may provide interfaces that enable a client system 130, asocial-networking system 160, or a third-party system 170 to manage,retrieve, modify, add, or delete, the information stored in data store164.

In particular embodiments, social-networking system 160 may store one ormore social graphs in one or more data stores 164. In particularembodiments, a social graph may include multiple nodes—which may includemultiple user nodes (each corresponding to a particular user) ormultiple concept nodes (each corresponding to a particular concept)—andmultiple edges connecting the nodes. Social-networking system 160 mayprovide users of the online social network the ability to communicateand interact with other users. In particular embodiments, users may jointhe online social network via social-networking system 160 and then addconnections (e.g., relationships) to a number of other users ofsocial-networking system 160 whom they want to be connected to. Herein,the term “friend” may refer to any other user of social-networkingsystem 160 with whom a user has formed a connection, association, orrelationship via social-networking system 160.

In particular embodiments, social-networking system 160 may provideusers with the ability to take actions on various types of items orobjects, supported by social-networking system 160. As an example andnot by way of limitation, the items and objects may include groups orsocial networks to which users of social-networking system 160 maybelong, events or calendar entries in which a user might be interested,computer-based applications that a user may use, transactions that allowusers to buy or sell items via the service, interactions withadvertisements that a user may perform, or other suitable items orobjects. A user may interact with anything that is capable of beingrepresented in social-networking system 160 or by an external system ofthird-party system 170, which is separate from social-networking system160 and coupled to social-networking system 160 via a network 110. Inparticular embodiments, social-networking system 160 may be capable oflinking a variety of entities. As an example and not by way oflimitation, social-networking system 160 may enable users to interactwith each other as well as receive content from third-party systems 170or other entities, or to allow users to interact with these entitiesthrough an application programming interfaces (API) or othercommunication channels.

In particular embodiments, a third-party system 170 may include one ormore types of servers, one or more data stores, one or more interfaces,including but not limited to APIs, one or more web services, one or morecontent sources, one or more networks, or any other suitable components,e.g., that servers may communicate with. A third-party system 170 may beoperated by a different entity from an entity operatingsocial-networking system 160. In particular embodiments, however,social-networking system 160 and third-party systems 170 may operate inconjunction with each other to provide social-networking services tousers of social-networking system 160 or third-party systems 170. Inthis sense, social-networking system 160 may provide a platform, orbackbone, which other systems, such as third-party systems 170, may useto provide social-networking services and functionality to users acrossthe Internet.

In particular embodiments, a third-party system 170 may include athird-party content object provider. A third-party content objectprovider may include one or more sources of content objects, which maybe communicated to a client system 130. As an example and not by way oflimitation, content objects may include information regarding things oractivities of interest to the user, such as, for example, movie showtimes, movie reviews, restaurant reviews, restaurant menus, productinformation and reviews, or other suitable information. As anotherexample and not by way of limitation, content objects may includeincentive content objects, such as coupons, discount tickets, giftcertificates, or other suitable incentive objects.

In particular embodiments, social-networking system 160 may include avariety of servers, sub-systems, programs, modules, logs, and datastores. In particular embodiments, social-networking system 160 mayinclude one or more of the following: a web server, action logger,API-request server, relevance-and-ranking engine, content-objectclassifier, notification controller, action log,third-party-content-object-exposure log, inference module,authorization/privacy server, search module, advertisement-targetingmodule, user-interface module, user-profile store, connection store,third-party content store, or location store. Social-networking system160 may also include suitable components such as network interfaces,security mechanisms, load balancers, failover servers,management-and-network-operations consoles, other suitable components,or any suitable combination thereof. In particular embodiments,social-networking system 160 may include one or more user-profile storesfor storing user profiles. A user profile may include, for example,biographic information, demographic information, behavioral information,social information, or other types of descriptive information, such aswork experience, educational history, hobbies or preferences, interests,affinities, or location. Interest information may include interestsrelated to one or more categories. Categories may be general orspecific. As an example and not by way of limitation, if a user “likes”an article about a brand of shoes the category may be the brand, or thegeneral category of “shoes” or “clothing.” A connection store may beused for storing connection information about users. The connectioninformation may indicate users who have similar or common workexperience, group memberships, hobbies, educational history, or are inany way related or share common attributes. The connection informationmay also include user-defined connections between different users andcontent (both internal and external). A web server may be used forlinking social-networking system 160 to one or more client systems 130or one or more third-party system 170 via network 110. The web servermay include a mail server or other messaging functionality for receivingand routing messages between social-networking system 160 and one ormore client systems 130. An API-request server may allow a third-partysystem 170 to access information from social-networking system 160 bycalling one or more APIs. An action logger may be used to receivecommunications from a web server about a user's actions on or offsocial-networking system 160. In conjunction with the action log, athird-party-content-object log may be maintained of user exposure tothird-party-content objects. A notification controller may provideinformation regarding content objects to a client system 130.Information may be pushed to a client system 130 as notifications, orinformation may be pulled from client system 130 responsive to a requestreceived from client system 130. Third-party-content-object stores maybe used to store content objects received from third parties, such as athird-party system 170. Location stores may be used for storing locationinformation received from client systems 130 associated with users.Advertisement-pricing modules may combine social information, thecurrent time, location information, or other suitable information toprovide relevant advertisements, in the form of notifications, to auser.

Social-networking system 160 may generate, store, receive, and sendsocial-networking data, such as, for example, user-profile data,concept-profile data, social-graph information, or other suitable datarelated to the online social network. In particular embodiments,social-networking system 160 also includes user-generated contentobjects, which may enhance a user's interactions with social-networkingsystem 160. User-generated content may include anything a user can add,upload, send, or “post” to social-networking system 160. As an exampleand not by way of limitation, a user communicates posts tosocial-networking system 160 from a client system 130. Posts may includedata such as status updates or other textual data, location information,photos, videos, links, music or other similar data or media. Content mayalso be added to social-networking system 160 by a third-party through a“communication channel,” such as a newsfeed or stream. A collection ofdata (e.g. content objects) may be stored as a database that is dividedinto a number of partitions. Each partition may be stored on separateservers 162 or at separate physical locations. Partitions may bedistributed over a number of servers 162 (while each partition may beduplicated at geographically diverse locations), the partitioning mayalso improve performance and reliability in accessing the database. Adatabase may be partitioned by storing rows (or columns) of the databaseseparately (i.e. “sharding”). A database may also be partitioned byusing a hashing algorithm. A database may also be partitioned by somereal-world segmentation of the data held by the database (e.g. users ineach time zone of the United States). In particular embodiments, data orcontent objects may stored in a number of partitions, each partitionholding content objects of a single content object type.

In particular embodiments, a content object uploaded tosocial-networking system 160 may be stored in a data store 164. Datastore information associated with the uploaded or shared content object(e.g. users liking the received content object) may be stored by asearch index of social-networking system 160. As described below, aserver process of social-networking system 160 may update the searchindex of one or more data stores 164 in response to activity onsocial-networking system 160. In particular embodiments, auser-generated content object (e.g. an uploaded image) may correspond toa particular node of a social graph, described below, ofsocial-networking system 160. An edge connecting the particular node andanother node may indicate a relationship between the received object anda user (or concept) corresponding to the other node. As an example andnot by way of limitation, information associated with the content objector information of one or more edges connecting to a node correspondingto the content object in the social graph may be stored in one or moredata stores 164.

In particular embodiments, social-networking system 160 may include anauthorization server that allows users to opt in or opt out of havingtheir actions logged by social-networking system 160 or shared withother systems (e.g. third-party systems 170), such as, for example, bysetting appropriate privacy settings. The authorization server ofsocial-networking system 160 may be used to enforce one or more privacysettings of the users of social-networking system 160. A privacy settingof a user determines how particular information or content objectsassociated with the user can be shared. In particular embodiments, thecontent objects generated or shared by users and provided bysocial-networking system 160 for presentation as search results,described below, may be restricted by the privacy settings of users ofsocial-networking system 160.

FIG. 2 illustrates example partitioning of an example search index of asocial-networking system. Although this disclosure illustrates anddescribes performing a search query on a search index with particulartypes of content objects stored on a particular type of computingsystem, this disclosure contemplates searching a search index with anysuitable type of content stored on any suitable type of computingsystem. In particular embodiments, a user may submit a query to thesocial-network system by inputting text into query field of a userinterface (UI) of the social-networking system. As an example and not byway of limitation, a user may search for information relating to aspecific subject matter (e.g. users, concepts, external content orresource) by providing a phrase describing the subject matter, oftenreferred to as a “search query.” The social-networking system may thensearch one or more partitions 42 to identify content matching the searchquery. A search may be conducted based on the query phrase using varioussearch algorithms and generate search results that identify resources orcontent (e.g. user-profile pages, content-profile pages, or externalresources) that are most likely to be related to the search query. Inresponse, the search may identify content or content objects that arelikely to be related to the search query, each of which may individuallybe referred to as a “search result,” or collectively be referred to asthe “search results” corresponding to the search query. The identifiedcontent or content objects may include, for example, social-graphelements (i.e. user nodes, concept nodes, or edges), profile pages,external webpages, or any combination thereof. This disclosurecontemplates any suitable object types for a social-networking system.

In the example of FIG. 2, one or more of partitions 42 may index contentobjects of the social networking system. As an example and not by way oflimitation, each content object or user of the social-networking systemmay be indexed based at least in part on a identifier information, suchas for example an unique identification number. In particularembodiments, each partition 42 may be configured to access identifierinformation for content objects stored in respective data storagedevices. Content objects stored in each partition 42 may be indexed by asearch index of the social-networking system. In particular embodiments,the portion of the search index associated with each partition 42 may beaccessed by one or more index servers 48 or one or more term servers 46.Term servers 46 described herein may, where appropriate, refer to a termdatabase server and index servers 48 may refer to an index databaseserver. A database server may provide database services for clientsystems accessing the social-networking system. Furthermore, each indexserver 48 or term 46 server may comprise a process executed on one ormore computing devices (e.g. server devices 162 described above) and maybe executed on the same computing device.

In particular embodiments, term 46 and index 48 servers may includeidentifier information associated with one or more content object typesdescribed above. In particular embodiments, term servers 46 may organizethe respective portion of the search index into posting lists associatedwith identifier information for content objects encompassingsubstantially all content objects types (e.g. images, video, statusupdates, or “likes”) “posted” on the social-networking system that areassociated with a particular search term or “term sharding.”Furthermore, the search terms encompassed by the posting lists of termservers 46 may be limited to those with a number of content objectsassociated with each search term or “hits” below a pre-determinedhit-threshold number. In particular embodiments, index servers 48 mayorganize the respective portion of the search index into posting listswith identifier information corresponding to content objects of aparticular content object type (e.g. images) “posted” on thesocial-networking system that are associated with a particular searchterm or “doc sharding.” Furthermore, the posting list of each indexserver 48 may include identifier information corresponding to a numberof content objects associated with the particular search term above thepre-determined hit-threshold number.

In particular embodiments, the pre-determined hit-threshold number mayvary based at least in part on a content-object type, such as forexample people, photos, or events, or the particular search term. As anexample and not by way of limitation, the pre-determined hit-thresholdnumber may be determined by a number of “hits” contained within apre-determined percentage (e.g. 99%) of each search term. In particularembodiments, the pre-determined hit-threshold number may be determinedbased at least in part on an index-to-term-server allocation ratio ofcomputing devices (e.g. servers), latency or throughput analysis ofvarying the pre-determined hit-threshold number, an aggregate networkutilization for sending term server 46 posting lists to or frompartition aggregators 44, a frequency of search queries containing aparticular search term, the frequency of live updates for a particularsearch term, constraints specific to a particular family of searchterms, or any combination thereof. As an example and not by way oflimitation, a constraint specific to a particular family of search termsmay be if a user is allowed to have up to 5000 friends, then thepre-determined hit-threshold number for search term “friend” may be setto 5000, such that all “friend” posting lists are contained in termservers 46.

In particular embodiments, a top aggregator 40 may be configured toreceive a search query that is distributed to a partition aggregator 44of each partition 42. As an example and not by way of limitation, asearch query may be implemented as a server process hosted by one ormore computing devices (e.g. servers 162 described above) of thesocial-networking system. As an example and not by way of limitation,top aggregator 40 may parse a search query “Gangnam Style” into searchterms, such as for example (<Gangnam><style>), that may return searchresults of any content object type that may match the search query.

In particular embodiments, top aggregator 40 may classify each searchterm based on a list (e.g. a hash set) of search terms with a number ofcontent objects above the pre-determined hit-threshold number. “Short”search terms described herein may, where appropriate, refer to a searchterm not contained in the hash set and “long” search terms may refer toa search term that is contained in the hash set. In particularembodiments, a partition aggregator 44 of each partition 42 may parsethe search query from top aggregator 40 and extract particular “short”search terms relevant to partition 42 from the search query. Inparticular embodiments, extraction of one or more “long” search termscontained in the hash set corresponding to search terms relevant topartition 42 may be performed by partition aggregator 44 of eachpartition 42. As an example and not by way of limitation, search query“Gangnam style” may be may be parsed by top aggregator 40 into searchterms <Gangnam> and <Style>. Furthermore, search term <Gangham> may notbe contained in the hash set and may be considered a “short” searchterm, while <style> may be contained in the hash set and may beconsidered a “long” search term. In particular embodiments, partitionaggregator 44 receiving the search terms from top aggregator 40 mayexecute a particular function to map the particular “short” search terms(e.g. <Gangham>) to a query to one or more of the term servers 46. Inparticular embodiments, partition aggregator 44 may retrieve one or moreposting lists from one or more term servers 46 that include informationidentifying particular content objects “posted” on the social-networkingsystem that correspond to the particular “short” search terms.

In particular embodiments, extraction of one or more “long” search termscontained in the hash set corresponding to search terms relevant topartition 42 may be performed by partition aggregator 44 of eachpartition 42. As an example and not by way of limitation, search query“Gangnam style” may be parsed by top aggregator 40 into search terms<Gangnam> and <Style>. In particular embodiments, partition aggregator44 receiving the search terms from top aggregator 40 may execute aparticular function to map the particular “short” search terms sent to aquery to one or more of the term servers 46. In particular embodiments,partition aggregator 44 may retrieve one or more posting lists from oneor more term servers 46 that include information identifying particularcontent objects “posted” on the social-networking system that correspondto the particular “short” search terms. Term servers 46 may send theretrieved posting lists corresponding to the particular “short” searchterms to partition aggregator 44.

In particular embodiments, the search query from top aggregator 40 maybe modified by each partition aggregator 44 to replace one or more“short” search terms with the one or more of the posting lists from termservers 46 that correspond to the “short” search terms. As an exampleand not by way of limitation, the modified search query may be generatedbased on the posting lists from term servers 46, such as for example<style>:<5, 7, 10>. In particular embodiments, partition aggregator 44may send the modified search query to corresponding index servers 48.Partition aggregator 44 may receive one or more posting lists from oneor more index servers 48 that include information identifying particularcontent objects “posted” on the social-networking system that correspondto the particular “long” search terms and search results from termservers 46. As an example and not by way of limitation, posting lists onindex servers 48 corresponding to search term <style> may includeidentifier information corresponding to content items <3, 4, 7, 10> andthe result of the modified search query may be <7,10>.

In another embodiment, partition aggregator 44 of each partition 42 maynot store information associated with “long” or “short” search terms.Instead partition aggregator 44 may send all of the parsed search termsto associated term servers 46. In particular embodiments, term servers46 may include a list of “short” and “long” search terms. As an exampleand not by way of limitation, each search term sent to term servers 46may return one or more posting lists that include informationidentifying particular content objects “posted” on the social-networkingsystem that correspond to the particular “short” search terms.Furthermore, term servers 46 may return a flag indicating that one ormore of parsed search terms are “long” search terms and the query forthe “long” search terms should be routed to index servers 48. Inparticular embodiments, the query for the “long” search terms may berouted to index servers 48 through partition aggregator 44. Inparticular embodiments, the query for the “long” search terms may berouted directly to index servers 48 by term servers 46. As describedabove, index servers 48 may retrieve one or more posting lists from oneor more index servers 48 that include information identifying particularcontent objects “posted” on the social-networking system that correspondto the particular “long” search terms.

In particular embodiments, top aggregator 40 may perform one or moreoperations on the search results received from partition aggregators 40.As an example and not by way of limitation, top aggregator 40 may returna search result to the user that is an intersection of the searchresults of all the search terms from term 46 and index 48 servers. Forexample, the query of term server 46 for search results corresponding tothe search term <Gangnam> may yield identifier information <5, 7, 10>that corresponds to particular content objects posted on thesocial-networking system. As another example, index servers 48 may yieldidentifier information corresponding to content items <3, 4, 7, 10> forsearch term <style>. Based on the intersection of the search resultssent to partition aggregator 44 from term 46 and index 48 servers 48 ofpartitions 42, the search result returned to the user may be <7, 10>.

In particular embodiments, the social-networking system may update oneor more partitions 42 of the search index based at least in part onactivity by users on the social-networking system, such as for examplecontent objects (e.g. an image) being uploaded or generated, or activity(e.g. “liking” or commenting) associated with a content object.Furthermore, one or more partitions 42 of the search index may beupdated at pre-determined intervals, such as for example once a week. Inparticular embodiments, the posting lists of each index server 48 mayinclude a base layer with identifier information that may be updated atthe pre-determined intervals and an update layer with identifierinformation that may be updated in response to activity on thesocial-networking system, such as new content objects being uploaded tothe social-networking system. As an example and not by way oflimitation, queries with “long” search terms sent to index servers 48may access the posting list that includes identifier information of thebase layer as well as identifier information of the update layercorresponding to recent activity on the social-networking systemdescribed above. In particular embodiments, the identifier informationof the base layer may be updated to include identifier information ofthe update layer during the pre-determined interval. Furthermore, theupdate layer may be returned to an initial state subsequent to updatingthe identifier information of the base layer with the identifierinformation of the update layer. In particular embodiments, identifierinformation of the posting list of term servers 44 may be periodicallyupdated to include recent activity that occurred during thepre-determined interval.

In particular embodiments, identifier information of the update layermay indicate deletion of a content object as a search result associatedwith a particular search term in response to a change of state of thecorresponding content object, such as for example deletion or “unliking”of the content object. In particular embodiments, index server 48 mayprovide information distinguishing between identifier informationprovided from the base layer from identifier information provided by theupdate layer. In particular embodiments, partition aggregator 42 maydetermine the intersection of identifier information provided by termservers 46 for the “short” term queries and by index servers 48 for the“long” search term queries. Furthermore, partition aggregator 42 mayintegrate identifier information from the update layer of term servers46 with the intersection of identifier information provided by termservers 46 and index servers 48. As example and not by way oflimitation, a query of the search term <Gangnam> to respective termserver 46 may yield identifier information <5, 7, 10>, a query of thesearch term <style> to the base layer of the respective index servers 48may yield identifier information <3, 4, 7, 10>, and the intersection ofthe queries would be <7, 10>. Furthermore, if content object associatedwith identifier information <20> is added to the update layer of indexserver 48 associated with the search term <style>, query of the searchterm <style> may also yield <20> as a search result. As another example,activity on the social-networking system (e.g. deleting a contentobject) subsequent an update of the base layer of index server 48 mayremove the content object associated with identifier information <10>and indicate on the update layer that identifier information <10> isremoved. The search results from the query of the search terms<Gangham><style> may yield <7> after the deleted content object <10> isremoved from the search results.

In particular embodiments, the posting lists of each term 46 and index48 server may include a base layer with identifier information that maybe updated at the pre-determined intervals and an update layer withidentifier information that may be updated in response to activity onthe social-networking system, such as new content objects being uploadedto the social-networking system. In particular embodiments, one or moresearch terms associated with a recently uploaded content object may becompared with the hash list, described above, to determine whether theidentifier information is relevant to posting list of term servers 46,index servers 48, or both. As an example and not by way of limitation, adetermination that the recent activity is relevant to a “short” searchterm, the update layer of the respective term server 46 may be updatedwith the identifier information corresponding to the recently uploadedcontent object. As another example, a determination that the recentactivity is relevant to a “long” search term, the update layer of therespective index server 48 may be updated with the identifierinformation corresponding to the recently uploaded content object. Inparticular embodiments, identifier information corresponding to deletedto content objects may be broadcast to all partitions 42 and thecorresponding identifier information removed from all posting lists ofboth term 46 and index 48 servers that contain the particular identifierinformation.

In particular embodiments, the identifier information of a particularterm server 46 associated with a particular search term may be“promoted” to posting lists of one or more index servers 48 and theidentifier information removed from the posting list of the particularterm server 46 in response to the number of hits for a particular searchterm exceeding the pre-determined hit-threshold number. As an exampleand not by way of limitation, generation of one or more posting lists inone or more term servers 46 may be performed to accommodate the initialaddition of one or more search terms to the social-networking system. Asearch term may be “promoted” from term servers 46 to index servers 48based at least at least in part on the pre-determined hit-thresholdnumber. As an example and not by way of limitation, a posting list maybe generated for the new term in term server 46 posting list, as long asthe number of content objects of the posting list is less than thepre-determined hit-threshold number. Identifier informationcorresponding to the content objects of the posting list associated withthe newly added search terms may be marked with a content object type(e.g. image or status update) described above. A determination that thenumber of content objects of the posting list exceeds the pre-determinedhit-threshold number, portions of the posting list associated with thesearch term are distributed to the posting list of one or more indexservers 48 associated with the search term in accordance with thecontent object type of the content objects in the posting list of termservers 46 associated with the search term.

If a failure occurs during “promotion” of a search term, a newly activeserver can query one or more term servers 46 for the “promoted” searchterms. Once all identifier information associated with the “promoted”search term has been verified as successfully created in the relevantposting lists of index servers 48, the search term and its associatedposting list may be deleted from respective term server 46. As anexample and not by way of limitation, identifier information may bepushed from term server 46 to index server 48 to populate the postinglist of index server 48 associated with the search term.

In particular embodiments, a new base layer of term 46 and index 48servers may be performed through a rotation of idle computing devices(e.g. servers). When a computing device of the primary architecture goesdown, any requests sent to the particular computing device may bere-directed to a corresponding computing device in a backuparchitecture. Alternatively, any requests may be redirected to topaggregator 40 in the backup architecture may direct the requests to anappropriate computing device. Particular embodiments may facilitatehosting more than one term server 46, more than one index server 48, orany combination thereof on a single computing device. Computing devicemay be re-distributed on the backup architecture so that when a singlecomputing device in the primary architecture fails, requests to theparticular computing device are distributed amongst a plurality ofcomputing devices in the backup architecture. Computing devices may beorganized into logical groupings of computing device (e.g. full rack,half-rack, quarter-rack), including one spare logical group of computingdevices for replication. During replication or update, the logicalgroupings may be updated in round-robin fashion, where fresh data for alive logical grouping may be copied to the spare logical grouping.Requests to the live logical grouping may re-directed to the sparelogical grouping, and then the live logical grouping becomes the sparelogical grouping.

In particular embodiments, top aggregator 40 may aggregate theidentifier information corresponding to particular content objects intoone or more search results provided by each partition aggregator 44 forpresentation to the user. In particular embodiments, top aggregator 40may aggregate search results of the respective search queries sent toeach partition 42. As an example and not by way of limitation, topaggregator 40 may perform an OR operation on the search query results toyield a set of final search results. The social-networking system mayrank the content objects that form the search results, such as forexample by a number of edges (i.e. a number of known relationships)connecting to a node corresponding to the particular object in thesocial graph. As an example and not by way of limitation, thesocial-networking system may rank an image by a number of “likes”associated with the image. As another example, the social-networkingsystem may also rank the image by a number of users tagged on the image.

FIG. 3 illustrates an example method for an example search with anupdate layer. The method may start at step 300, where one or morecomputing devices receive an update of activity associated with one ormore content objects associated with a search term. In particularembodiments, the search term is associated with a number of contentobjects that exceeds a pre-determined threshold number. In particularembodiments, the content objects associated with the search term areindexed on a list of one or more index servers. The list includesidentifier information that corresponds to the content objects. At step302, one or more computing devices modify the list of one or more of theindex servers in response to the update, at which point the method mayend. Although this disclosure describes and illustrates particular stepsof the method of FIG. 3 as occurring in a particular order, thisdisclosure contemplates any suitable steps of the method of FIG. 3occurring in any suitable order. Moreover, although this disclosuredescribes and illustrates particular components carrying out particularsteps of the method of FIG. 3, this disclosure contemplates any suitablecombination of any suitable components carrying out any suitable stepsof the method of FIG. 3.

FIG. 4 illustrates an example method for an example search withincorporated updates. The method may start at step 350, where one ormore computing devices receive an update of activity associated with oneor more content objects associated with a search term. In particularembodiments, the content objects are associated with the search termbeing indexed on a list of one or more index servers or a term server.In particular embodiments, the list of the term server may includeidentifier information of one or more content object types. The list ofthe index servers may include identifier information of a single contentobject type. Step 352, by one or more computing devices, determinewhether the search term has a number of associated content objectsexceeding a pre-determined threshold number. At step 354, one or morecomputing devices modifies the list associated with the search term of aterm server or one or more of the index servers based at least in parton the determination and in response to the update, at which point themethod may end. Although this disclosure describes and illustratesparticular steps of the method of FIG. 4 as occurring in a particularorder, this disclosure contemplates any suitable steps of the method ofFIG. 4 occurring in any suitable order. Moreover, although thisdisclosure describes and illustrates particular components carrying outparticular steps of the method of FIG. 4, this disclosure contemplatesany suitable combination of any suitable components carrying out anysuitable steps of the method of FIG. 4.

FIG. 5 illustrates an example social graph. In particular embodiments,social-networking system 160 may store one or more social graphs 200 inone or more data stores. In particular embodiments, social graph 200 mayinclude multiple nodes—which may include multiple user nodes 202 ormultiple concept nodes 204—and multiple edges 206 connecting the nodes.Example social graph 200 illustrated in FIG. 5 is shown, for didacticpurposes, in a two-dimensional visual map representation. In particularembodiments, a social-networking system 160, client system 130, orthird-party system 170 may access social graph 200 and relatedsocial-graph information for suitable applications. The nodes and edgesof social graph 200 may be stored as data objects, for example, in adata store (such as a social-graph database). Such a data store mayinclude one or more searchable or queryable indexes of nodes or edges ofsocial graph 200.

In particular embodiments, a user node 202 may correspond to a user ofsocial-networking system 160. As an example and not by way oflimitation, a user may be an individual (human user), an entity (e.g. anenterprise, business, or third-party application), or a group (e.g. ofindividuals or entities) that interacts or communicates with or oversocial-networking system 160. In particular embodiments, when a userregisters for an account with social-networking system 160,social-networking system 160 may create a user node 202 corresponding tothe user, and store the user node 202 in one or more data stores. Usersand user nodes 202 described herein may, where appropriate, refer toregistered users and user nodes 202 associated with registered users. Inaddition or as an alternative, users and user nodes 202 described hereinmay, where appropriate, refer to users that have not registered withsocial-networking system 160. In particular embodiments, a user node 202may be associated with information provided by a user or informationgathered by various systems, including social-networking system 160. Asan example and not by way of limitation, a user may provide his or hername, profile picture, contact information, birth date, sex, maritalstatus, family status, employment, education background, preferences,interests, or other demographic information. In particular embodiments,a user node 202 may be associated with one or more data objectscorresponding to information associated with a user. In particularembodiments, a user node 202 may correspond to one or more webpages.

In particular embodiments, a concept node 204 may correspond to aconcept. As an example and not by way of limitation, a concept maycorrespond to a place (such as, for example, a movie theater,restaurant, landmark, or city); a website (such as, for example, awebsite associated with social-network system 160 or a third-partywebsite associated with a web-application server); an entity (such as,for example, a person, business, group, sports team, or celebrity); aresource (such as, for example, an audio file, video file, digitalphoto, text file, structured document, or application) which may belocated within social-networking system 160 or on an external server,such as a web-application server; real or intellectual property (suchas, for example, a sculpture, painting, movie, game, song, idea,photograph, or written work); a game; an activity; an idea or theory;another suitable concept; or two or more such concepts. A concept node204 may be associated with information of a concept provided by a useror information gathered by various systems, including social-networkingsystem 160. As an example and not by way of limitation, information of aconcept may include a name or a title; one or more images (e.g. an imageof the cover page of a book); a location (e.g. an address or ageographical location); a website (which may be associated with a URL);contact information (e.g. a phone number or an email address); othersuitable concept information; or any suitable combination of suchinformation. In particular embodiments, a concept node 204 may beassociated with one or more data objects corresponding to informationassociated with concept node 204. In particular embodiments, a conceptnode 204 may correspond to one or more webpages.

In particular embodiments, a node in social graph 200 may represent orbe represented by a webpage (which may be referred to as a “profilepage”). Profile pages may be hosted by or accessible tosocial-networking system 160. Profile pages may also be hosted onthird-party websites associated with a third-party server 170. As anexample and not by way of limitation, a profile page corresponding to aparticular external webpage may be the particular external webpage andthe profile page may correspond to a particular concept node 204.Profile pages may be viewable by all or a selected subset of otherusers. As an example and not by way of limitation, a user node 202 mayhave a corresponding user-profile page in which the corresponding usermay add content, make declarations, or otherwise express himself orherself. As another example and not by way of limitation, a concept node204 may have a corresponding concept-profile page in which one or moreusers may add content, make declarations, or express themselves,particularly in relation to the concept corresponding to concept node204.

In particular embodiments, a concept node 204 may represent athird-party webpage or resource hosted by a third-party system 170. Thethird-party webpage or resource may include, among other elements,content, a selectable or other icon, or other inter-actable object(which may be implemented, for example, in JavaScript, AJAX, or PHPcodes) representing an action or activity. As an example and not by wayof limitation, a third-party webpage may include a selectable icon suchas “like,” “check in,” “eat,” “recommend,” or another suitable action oractivity. A user viewing the third-party webpage may perform an actionby selecting one of the icons (e.g. “eat”), causing a client system 130to transmit to social-networking system 160 a message indicating theuser's action. In response to the message, social-networking system 160may create an edge (e.g. an “eat” edge) between a user node 202corresponding to the user and a concept node 204 corresponding to thethird-party webpage or resource and store edge 206 in one or more datastores.

In particular embodiments, a pair of nodes in social graph 200 may beconnected to each other by one or more edges 206. An edge 206 connectinga pair of nodes may represent a relationship between the pair of nodes.In particular embodiments, an edge 206 may include or represent one ormore data objects or attributes corresponding to the relationshipbetween a pair of nodes. As an example and not by way of limitation, afirst user may indicate that a second user is a “friend” of the firstuser. In response to this indication, social-networking system 160 maytransmit a “friend request” to the second user. If the second userconfirms the “friend request,” social-networking system 160 may createan edge 206 connecting the first user's user node 202 to the seconduser's user node 202 in social graph 200 and store edge 206 associal-graph information in one or more of data stores 24. In theexample of FIG. 5, social graph 200 includes an edge 206 indicating afriend relation between user nodes 202 of user “A” and user “B” and anedge indicating a friend relation between user nodes 202 of user “C” anduser “B.” Although this disclosure describes or illustrates particularedges 206 with particular attributes connecting particular user nodes202, this disclosure contemplates any suitable edges 206 with anysuitable attributes connecting user nodes 202. As an example and not byway of limitation, an edge 206 may represent a friendship, familyrelationship, business or employment relationship, fan relationship,follower relationship, visitor relationship, subscriber relationship,superior/subordinate relationship, reciprocal relationship,non-reciprocal relationship, another suitable type of relationship, ortwo or more such relationships. Moreover, although this disclosuregenerally describes nodes as being connected, this disclosure alsodescribes users or concepts as being connected. Herein, references tousers or concepts being connected may, where appropriate, refer to thenodes corresponding to those users or concepts being connected in socialgraph 200 by one or more edges 206.

In particular embodiments, an edge 206 between a user node 202 and aconcept node 204 may represent a particular action or activity performedby a user associated with user node 202 toward a concept associated witha concept node 204. As an example and not by way of limitation, asillustrated in FIG. 5, a user may “like,” “attended,” “played,”“listened,” “cooked,” “worked at,” or “watched” a concept, each of whichmay correspond to a edge type or subtype. A concept-profile pagecorresponding to a concept node 204 may include, for example, aselectable “check in” icon (such as, for example, a clickable “check in”icon) or a selectable “like” icon. As another example, the socializeddash of a client system may include a selectable “check in” icon (suchas, for example, a clickable “check in” icon) or a selectable “like”icon. Similarly, after a user clicks these icons, social-networkingsystem 160 may create a “like” edge or a “check in” edge in response toa user's action corresponding to a respective action. As another exampleand not by way of limitation, a user (user “C”) may listen to aparticular song (“Ramble On”) using a particular application (SPOTIFY,which is an online music application). In this case, social-networkingsystem 160 may create a “listened” edge 206 and a “used” edge (asillustrated in FIG. 5) between user nodes 202 corresponding to the userand concept nodes 204 corresponding to the song and application toindicate that the user listened to the song and used the application.Moreover, social-networking system 160 may create a “played” edge 206(as illustrated in FIG. 5) between concept nodes 204 corresponding tothe song and the application to indicate that the particular song wasplayed by the particular application. In this case, “played” edge 206corresponds to an action performed by an external application (SPOTIFY)on an external audio file (the song “Imagine”). Although this disclosuredescribes particular edges 206 with particular attributes connectinguser nodes 202 and concept nodes 204, this disclosure contemplates anysuitable edges 206 with any suitable attributes connecting user nodes202 and concept nodes 204. Moreover, although this disclosure describesedges between a user node 202 and a concept node 204 representing asingle relationship, this disclosure contemplates edges between a usernode 202 and a concept node 204 representing one or more relationships.As an example and not by way of limitation, an edge 206 may representboth that a user likes and has used at a particular concept.Alternatively, another edge 206 may represent each type of relationship(or multiples of a single relationship) between a user node 202 and aconcept node 204 (as illustrated in FIG. 5 between user node 202 foruser “E” and concept node 204 for “SPOTIFY”).

In particular embodiments, social-networking system 160 may create anedge 206 between a user node 202 and a concept node 204 in social graph200. As an example and not by way of limitation, a user viewing aconcept-profile page (such as, for example, by using a web browser or aspecial-purpose application hosted by the user's client system 130) mayindicate that he or she likes the concept represented by the conceptnode 204 by clicking or selecting a “Like” icon, which may cause theuser's client system 130 to transmit to social-networking system 160 amessage indicating the user's liking of the concept associated with theconcept-profile page. In response to the message, social-networkingsystem 160 may create an edge 206 between user node 202 associated withthe user and concept node 204, as illustrated by “like” edge 206 betweenthe user and concept node 204. In particular embodiments,social-networking system 160 may store an edge 206 in one or more datastores. In particular embodiments, an edge 206 may be automaticallyformed by social-networking system 160 in response to a particular useraction. As an example and not by way of limitation, if a first useruploads a picture, watches a movie, or listens to a song, an edge 206may be formed between user node 202 corresponding to the first user andconcept nodes 204 corresponding to those concepts. Although thisdisclosure describes forming particular edges 206 in particular manners,this disclosure contemplates forming any suitable edges 206 in anysuitable manner.

FIG. 6 illustrates example computing system. In particular embodiments,one or more computer systems 60 perform one or more steps of one or moremethods described or illustrated herein. In particular embodiments, oneor more computer systems 60 provide functionality described orillustrated herein. In particular embodiments, software running on oneor more computer systems 60 performs one or more steps of one or moremethods described or illustrated herein or provides functionalitydescribed or illustrated herein. Particular embodiments include one ormore portions of one or more computer systems 60. Herein, reference to acomputer system may encompass a computing device, where appropriate.Moreover, reference to a computer system may encompass one or morecomputer systems, where appropriate.

This disclosure contemplates any suitable number of computer systems 60.This disclosure contemplates computer system 60 taking any suitablephysical form. As example and not by way of limitation, computer system60 may be an embedded computer system, a system-on-chip (SOC), asingle-board computer system (SBC) (such as, for example, acomputer-on-module (COM) or system-on-module (SOM)), a desktop computersystem, a laptop or notebook computer system, an interactive kiosk, amainframe, a mesh of computer systems, a mobile telephone, a personaldigital assistant (PDA), a server, a tablet computer system, or acombination of two or more of these. Where appropriate, computer system60 may include one or more computer systems 60; be unitary ordistributed; span multiple locations; span multiple machines; spanmultiple data centers; or reside in a cloud, which may include one ormore cloud components in one or more networks. Where appropriate, one ormore computer systems 60 may perform without substantial spatial ortemporal limitation one or more steps of one or more methods describedor illustrated herein. As an example and not by way of limitation, oneor more computer systems 60 may perform in real time or in batch modeone or more steps of one or more methods described or illustratedherein. One or more computer systems 60 may perform at different timesor at different locations one or more steps of one or more methodsdescribed or illustrated herein, where appropriate.

In particular embodiments, computer system 60 includes a processor 62,memory 64, storage 66, an input/output (I/O) interface 68, acommunication interface 70, and a bus 72. Although this disclosuredescribes and illustrates a particular computer system having aparticular number of particular components in a particular arrangement,this disclosure contemplates any suitable computer system having anysuitable number of any suitable components in any suitable arrangement.

In particular embodiments, processor 62 includes hardware for executinginstructions, such as those making up a computer program. As an exampleand not by way of limitation, to execute instructions, processor 62 mayretrieve (or fetch) the instructions from an internal register, aninternal cache, memory 64, or storage 66; decode and execute them; andthen write one or more results to an internal register, an internalcache, memory 64, or storage 66. In particular embodiments, processor 62may include one or more internal caches for data, instructions, oraddresses. This disclosure contemplates processor 62 including anysuitable number of any suitable internal caches, where appropriate. Asan example and not by way of limitation, processor 62 may include one ormore instruction caches, one or more data caches, and one or moretranslation lookaside buffers (TLBs). Instructions in the instructioncaches may be copies of instructions in memory 64 or storage 66, and theinstruction caches may speed up retrieval of those instructions byprocessor 62. Data in the data caches may be copies of data in memory 64or storage 66 for instructions executing at processor 62 to operate on;the results of previous instructions executed at processor 62 for accessby subsequent instructions executing at processor 62 or for writing tomemory 64 or storage 66; or other suitable data. The data caches mayspeed up read or write operations by processor 62. The TLBs may speed upvirtual-address translation for processor 62. In particular embodiments,processor 62 may include one or more internal registers for data,instructions, or addresses. This disclosure contemplates processor 62including any suitable number of any suitable internal registers, whereappropriate. Where appropriate, processor 62 may include one or morearithmetic logic units (ALUs); be a multi-core processor; or include oneor more processors 62. Although this disclosure describes andillustrates a particular processor, this disclosure contemplates anysuitable processor.

In particular embodiments, memory 64 includes main memory for storinginstructions for processor 62 to execute or data for processor 62 tooperate on. As an example and not by way of limitation, computer system60 may load instructions from storage 66 or another source (such as, forexample, another computer system 60) to memory 64. Processor 62 may thenload the instructions from memory 64 to an internal register or internalcache. To execute the instructions, processor 62 may retrieve theinstructions from the internal register or internal cache and decodethem. During or after execution of the instructions, processor 62 maywrite one or more results (which may be intermediate or final results)to the internal register or internal cache. Processor 62 may then writeone or more of those results to memory 64. In particular embodiments,processor 62 executes only instructions in one or more internalregisters or internal caches or in memory 64 (as opposed to storage 66or elsewhere) and operates only on data in one or more internalregisters or internal caches or in memory 64 (as opposed to storage 66or elsewhere). One or more memory buses (which may each include anaddress bus and a data bus) may couple processor 62 to memory 64. Bus 72may include one or more memory buses, as described below. In particularembodiments, one or more memory management units (MMUs) reside betweenprocessor 62 and memory 64 and facilitate accesses to memory 64requested by processor 62. In particular embodiments, memory 64 includesrandom access memory (RAM). This RAM may be volatile memory, whereappropriate Where appropriate, this RAM may be dynamic RAM (DRAM) orstatic RAM (SRAM). Moreover, where appropriate, this RAM may besingle-ported or multi-ported RAM. This disclosure contemplates anysuitable RAM. Memory 64 may include one or more memories 64, whereappropriate. Although this disclosure describes and illustratesparticular memory, this disclosure contemplates any suitable memory.

In particular embodiments, storage 66 includes mass storage for data orinstructions. As an example and not by way of limitation, storage 66 mayinclude a hard disk drive (HDD), a floppy disk drive, flash memory, anoptical disc, a magneto-optical disc, magnetic tape, or a UniversalSerial Bus (USB) drive or a combination of two or more of these. Storage66 may include removable or non-removable (or fixed) media, whereappropriate. Storage 66 may be internal or external to computer system60, where appropriate. In particular embodiments, storage 66 isnon-volatile, solid-state memory. In particular embodiments, storage 66includes read-only memory (ROM). Where appropriate, this ROM may bemask-programmed ROM, programmable ROM (PROM), erasable PROM (EPROM),electrically erasable PROM (EEPROM), electrically alterable ROM (EAROM),or flash memory or a combination of two or more of these. Thisdisclosure contemplates mass storage 66 taking any suitable physicalform. Storage 66 may include one or more storage control unitsfacilitating communication between processor 62 and storage 66, whereappropriate. Where appropriate, storage 66 may include one or morestorages 66. Although this disclosure describes and illustratesparticular storage, this disclosure contemplates any suitable storage.

In particular embodiments, I/O interface 68 includes hardware, software,or both providing one or more interfaces for communication betweencomputer system 60 and one or more I/O devices. Computer system 60 mayinclude one or more of these I/O devices, where appropriate. One or moreof these I/O devices may enable communication between a person andcomputer system 60. As an example and not by way of limitation, an I/Odevice may include a keyboard, keypad, microphone, monitor, mouse,printer, scanner, speaker, still camera, stylus, tablet, touch screen,trackball, video camera, another suitable I/O device or a combination oftwo or more of these. An I/O device may include one or more sensors.This disclosure contemplates any suitable I/O devices and any suitableI/O interfaces 68 for them. Where appropriate, I/O interface 68 mayinclude one or more device or software drivers enabling processor 62 todrive one or more of these I/O devices. I/O interface 68 may include oneor more I/O interfaces 68, where appropriate. Although this disclosuredescribes and illustrates a particular I/O interface, this disclosurecontemplates any suitable I/O interface.

In particular embodiments, communication interface 70 includes hardware,software, or both providing one or more interfaces for communication(such as for example, packet-based communication) between computersystem 60 and one or more other computer systems 60 or one or morenetworks. As an example and not by way of limitation, communicationinterface 70 may include a network interface controller (NIC) or networkadapter for communicating with an Ethernet or other wire-based networkor a wireless NIC (WNIC) or wireless adapter for communicating with awireless network, such as a WI-FI network. This disclosure contemplatesany suitable network and any suitable communication interface 70 for it.As an example and not by way of limitation, computer system 60 maycommunicate with an ad hoc network, a personal area network (PAN), alocal area network (LAN), a wide area network (WAN), a metropolitan areanetwork (MAN), or one or more portions of the Internet or a combinationof two or more of these. One or more portions of one or more of thesenetworks may be wired or wireless. As an example, computer system 60 maycommunicate with a wireless PAN (WPAN) (such as for example, a BLUETOOTHWPAN), a WI-FI network, a WI-MAX network, a cellular telephone network(such as, for example, a Global System for Mobile Communications (GSM)network), or other suitable wireless network or a combination of two ormore of these. Computer system 60 may include any suitable communicationinterface 70 for any of these networks, where appropriate. Communicationinterface 70 may include one or more communication interfaces 70, whereappropriate. Although this disclosure describes and illustrates aparticular communication interface, this disclosure contemplates anysuitable communication interface.

In particular embodiments, bus 72 includes hardware, software, or bothcoupling components of computer system 60 to each other. As an exampleand not by way of limitation, bus 72 may include an Accelerated GraphicsPort (AGP) or other graphics bus, an Enhanced Industry StandardArchitecture (EISA) bus, a front-side bus (FSB), a HYPERTRANSPORT (HT)interconnect, an Industry Standard Architecture (ISA) bus, an INFINIBANDinterconnect, a low-pin-count (LPC) bus, a memory bus, a Micro ChannelArchitecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, aPCI-Express (PCIe) bus, a serial advanced technology attachment (SATA)bus, a Video Electronics Standards Association local (VLB) bus, oranother suitable bus or a combination of two or more of these. Bus 72may include one or more buses 72, where appropriate. Although thisdisclosure describes and illustrates a particular bus, this disclosurecontemplates any suitable bus or interconnect.

Herein, a computer-readable non-transitory storage medium or media mayinclude one or more semiconductor-based or other integrated circuits(ICs) (such, as for example, field-programmable gate arrays (FPGAs) orapplication-specific ICs (ASICs)), hard disk drives (HDDs), hybrid harddrives (HHDs), optical discs, optical disc drives (ODDs),magneto-optical discs, magneto-optical drives, floppy diskettes, floppydisk drives (FDDs), magnetic tapes, solid-state drives (SSDs),RAM-drives, SECURE DIGITAL cards or drives, any other suitablecomputer-readable non-transitory storage media, or any suitablecombination of two or more of these, where appropriate. Acomputer-readable non-transitory storage medium may be volatile,non-volatile, or a combination of volatile and non-volatile, whereappropriate.

Herein, “or” is inclusive and not exclusive, unless expressly indicatedotherwise or indicated otherwise by context. Therefore, herein, “A or B”means “A, B, or both,” unless expressly indicated otherwise or indicatedotherwise by context. Moreover, “and” is both joint and several, unlessexpressly indicated otherwise or indicated otherwise by context.Therefore, herein, “A and B” means “A and B, jointly or severally,”unless expressly indicated otherwise or indicated otherwise by context.

The scope of this disclosure encompasses all changes, substitutions,variations, alterations, and modifications to the example embodimentsdescribed or illustrated herein that a person having ordinary skill inthe art would comprehend. The scope of this disclosure is not limited tothe example embodiments described or illustrated herein. Moreover,although this disclosure describes and illustrates respectiveembodiments herein as including particular components, elements,functions, operations, or steps, any of these embodiments may includeany combination or permutation of any of the components, elements,functions, operations, or steps described or illustrated anywhere hereinthat a person having ordinary skill in the art would comprehend.Furthermore, reference in the appended claims to an apparatus or systemor a component of an apparatus or system being adapted to, arranged to,capable of, configured to, enabled to, operable to, or operative toperform a particular function encompasses that apparatus, system,component, whether or not it or that particular function is activated,turned on, or unlocked, as long as that apparatus, system, or componentis so adapted, arranged, capable, configured, enabled, operable, oroperative.

What is claimed is:
 1. A method comprising: by one or more computingdevices, receiving an update of activity associated with one or morecontent objects associated with a search term, the content objectsassociated with the search term being indexed on one or more indexservers or a term server, the term server comprising a list ofidentifier information of one or more content object types, each indexserver comprising a list identifier information of a single contentobject type; by one or more computing devices, determining whether thesearch term has a number of associated content objects exceeding apre-determined threshold number; and by one or more computing devices,modifying the list associated with the search term of a term server orone or more of the index servers based at least in part on thedetermination and in response to the update.
 2. The method of claim 1,wherein each list comprises a base layer and an update layer, identifierinformation of the base layer being updated at a pre-determinedinterval, identifier information of the update layer being updated priorto the pre-determined interval.
 3. The method of claim 2, wherein themodification comprises, by one or more computing devices, addingidentifier information of the content object associated with theactivity to the update layer of the list of one or more of the indexservers associated with the search term based at least in part on thenumber of content objects associated with the search term exceeding thepre-determined threshold number.
 4. The method of claim 2, wherein themodification comprises, by one or more computing devices, addingidentifier information of the content object associated with theactivity to the update layer of the list of the term server associatedwith the search term based at least in part on the number of contentobjects associated with the search term being less than thepre-determined threshold number.
 5. The method of claim 1, furthercomprises, by one or more computing devices, providing an indication tothe term and index servers that the content object associated with theactivity is no longer associated with the search term in response to theactivity deleting the content object.
 6. The method of claim 1, furthercomprises, by one or more computing devices, generating a new listassociated with a new search term on a particular term server inresponse to the new search term being added to a search index.
 7. Themethod of claim 1, further comprises: by one or more computing devices,receiving a search query comprising the search term and the other searchterm; by one or more computing devices, accessing the list of the termserver or one or more index servers associated with the search term andthe other search term based at least in part on the determination; byone or more computing devices, determining one or more search resultsbased at least in part on an intersection of the identifier informationof one or more lists associated with the search term and one or morelist associated with the other search term; and by one or more computingdevice, providing for presentation one or more content objectscorresponding to the search results of the search query.
 8. The methodof claim 1, further comprising: by one or more computing devices,generating a list associated with the search term on one or more indexservers in response to the number content objects associated with thesearch term exceeding the pre-determined threshold number due to theupdate; and by one or more computing devices, populating the list of oneor more of the index servers associated with the other search term withidentifier information of one or more content objects indexed by a termserver; and by one or more computing device, deleting the search termand a list associated with the search term from of the term server. 9.One or more computer-readable non-transitory storage media embodyingsoftware configured when executed to: receive an update of activityassociated with one or more content objects associated with a searchterm, the content objects associated with the search term being indexedon one or more index servers or a term server, the term servercomprising a list of identifier information of one or more contentobject types, each index server comprising a list identifier informationof a single content object type; determine whether the search term has anumber of associated content objects exceeding a pre-determinedthreshold number; and modify the list associated with the search term ofa term server or one or more of the index servers based at least in parton the determination and in response to the update.
 10. The media ofclaim 9, wherein each list comprises a base layer and an update layer,identifier information of the base layer being updated at apre-determined interval, identifier information of the update layerbeing updated prior to the pre-determined interval.
 11. The media ofclaim 10, wherein the software is further configured to add identifierinformation of the content object associated with the activity to theupdate layer of the list of one or more of the index servers associatedwith the search term based at least in part on the number of contentobjects associated with the search term exceeding the pre-determinedthreshold number.
 12. The media of claim 10, wherein the software isfurther configured to add identifier information of the content objectassociated with the activity to the update layer of the list of the termserver associated with the search term based at least in part on thenumber of content objects associated with the search term being lessthan the pre-determined threshold number.
 13. The media of claim 9,wherein the software is further configured to provide an indication tothe term and index servers that the content object associated with theactivity is no longer associated with the search term in response to theactivity deleting the content object.
 14. The media of claim 9, whereinthe software is further configured to generate a new list associatedwith a new search term on a particular term server in response to thenew search term being added to a search index.
 15. The media of claim 9,wherein the software is further configured to: receive a search querycomprising the search term and other search term; access the list of theterm server or one or more index servers associated with the search termand the other search term based at least in part on the determination;determine one or more search results based at least in part on anintersection of the identifier information of one or more listsassociated with the search term and one or more list associated with theother search term; and provide for presentation one or more contentobjects corresponding to the search results of the search query.
 16. Themedia of claim 9, wherein the software is further configured to:generate a list associated with the search term on one or more indexservers in response to the number content objects associated with thesearch term exceeding the pre-determined threshold number due to theupdate; and populate the list of one or more of the index serversassociated with the other search term with identifier information of oneor more content objects indexed by a term server; and delete the searchterm and a list associated with the search term from of the term server.17. A device comprising: a processor; and one or more computer-readablenon-transitory storage media coupled to the processor and embodyingsoftware that: receive an update of activity associated with one or morecontent objects associated with a search term, the content objectsassociated with the search term being indexed on one or more indexservers or a term server, the term server comprising a list ofidentifier information of one or more content object types, each indexserver comprising a list identifier information of a single contentobject type; determine whether the search term has a number ofassociated content objects exceeding a pre-determined threshold number;and modify the list associated with the search term of a term server orone or more of the index servers based at least in part on thedetermination and in response to the update.
 18. The device of claim 17,wherein each list comprises a base layer and an update layer, identifierinformation of the base layer being updated at a pre-determinedinterval, identifier information of the update layer being updated priorto the pre-determined interval.
 19. The device of claim 18, wherein thesoftware is further configured to add identifier information of thecontent object associated with the activity to the update layer of thelist of one or more of the index servers associated with the search termbased at least in part on the number of content objects associated withthe search term exceeding the pre-determined threshold number.
 20. Thedevice of claim 18, wherein the software is further configured to addidentifier information of the content object associated with theactivity to the update layer of the list of the term server associatedwith the search term based at least in part on the number of contentobjects associated with the search term being less than thepre-determined threshold number.